C

Fig. 7.8. Repair of arch dissection. (a) Bypass, cardiac arrest, and profound hypothermia with circulatory arrest are established. A graft is inserted with separate anastomosis of the distal aorta and arch vessels. The intimal tear is excluded. (b) The cross-clamp is applied to the proximal graft, and cardiopulmonary bypass and warming are resumed. The arch vessels are thus perfused while the proximal anastomosis is performed. (c) Alternatively, a beveled anastomosis is performed to include both the distal aorta and arch vessels.

suture plication, or reimplantation of the arch vessels as a separate pedicle or as part of a beveled distal anastomosis (Fig. 7.8). Deairing is performed by turning on the pump slowly, deairing the aorta from the transverse arch and ensuring air does not enter the arch vessels. Full bypass is re-established and the patient re-warmed while any unfinished proximal procedures (e.g., aortic valve replacement, coronary reimplantation) are performed.

Several technical points should be made. Generally for Marfan's, an aortic valve replacement as a valve conduit (Bentall or Cabrol procedure) should be done rather than a supracoronary conduit and separate aortic valve replacement. This is because of the chance of degeneration and aneurysmal dilation of the aortic segment containing the coronary orifices. If the dissection is not due to Marfan's syndrome, then an attempt is made to resuspend the valve and place a supracoronary graft without reimplanting the coronary arteries. The texture and "feel" of the aorta is an important factor in the surgeon's decision making process for the use of felt. Acute aortic dissections are extremely friable compared to the sturdier aneurysm walls and require meticulous suturing and felt reinforcement. For aortic dissection, a felt strip is placed within the aorta as well as another strip outside the aorta and secured with a whip stitch, then the Dacron tube graft separately sewn onto this (Fig. 7.9a). Another technique is to incorporate both the graft, outer felt, aorta, and inner felt as one continuous whip stitch (Fig. 7.9b).

OUTER FELT STRIP

INNER FELT ADDED

WHIP STITCH

COMPLETED GRAFT

OUTER FELT STRIP

INNER FELT ADDED

WHIP STITCH

COMPLETED GRAFT

PROXIMAL AORTA

PROXIMAL AORTA

GRAFT

DISTAL AORTA

Fig. 7.9. Methods of felt repair in acute aortic dissection. (a) Separate preparation of aortic ends with felt. An outer and inner layer of felt are anchored to the aorta with a whip stitch, and the graft is anastomosed to this. (b) Combined graft anastomosis with addition of felt. The entire anastomosis may be done at once with both strips of felt. The suture is placed from graft to outer felt to aorta to inner felt. 1: graft; 2: outer felt; 3: aorta; 4: inner felt.

GRAFT

DISTAL AORTA

Fig. 7.9. Methods of felt repair in acute aortic dissection. (a) Separate preparation of aortic ends with felt. An outer and inner layer of felt are anchored to the aorta with a whip stitch, and the graft is anastomosed to this. (b) Combined graft anastomosis with addition of felt. The entire anastomosis may be done at once with both strips of felt. The suture is placed from graft to outer felt to aorta to inner felt. 1: graft; 2: outer felt; 3: aorta; 4: inner felt.

Another technical point is that when performing the distal anastomosis in aortic dissection, the pump should be slowly turned on to be sure one is performing the anastomosis to the true lumen. If the true lumen has been sewn shut, no blood will be seen to come out of the lumen. In this case, a V-excision must be made between the true and false lumens as a type of fenestration.

Cerebral ischemia during the period of circulatory arrest is of paramount concern. Circulatory arrest times greater than 45-60 minutes dramatically increase the chances of neurologic sequelae. Techniques of cerebral protection include systemic cooling to 18°C, packing the head in ice, and intraoperative administration of mannitol, steroids, and free radical scavengers. Cerebral perfusion may be performed, either by the antegrade or retrograde route. In the antegrade route, a great vessel or one of its branches (e.g., right subclavian artery) is cannulated and cold blood administered during the circulatory arrest period. In the retrograde approach, the superior vena cava is cannulated and snared and cold blood administered retrogradely. These techniques appear to increase the "safe" period of circulatory arrest.

The tissues in acute aortic dissection are extraordinarily fragile, and felt strips have been historically used most often in the United States to reinforce these tissues. Several surgical glues are used in acute aortic dissections and have a threefold purpose: reinforcement of friable tissues, support of suture lines for hemo-stasis and obliteration of the false lumen in aortic dissection. Gelatin-resorcinal-

Fig. 7.10. Relative incidence of thoracic aneurysms.

formaldehyde (GRF) is the glue that has previously been used most commonly. Although the glue has a good track record, there are concerns about the high reoperation rate and tissue toxicity. An alternative is the recently introduced Bioglue Surgical Adhesive (CryoLife International, Inc., Kennesaw, GA, USA) consisting of 10% glutaraldehyde and 45% bovine serum albumin. Mixing the components occurs in situ at surgery, creating a strong scaffold through immediate polymerization and binding of lysine molecules. Within 2 minutes maximal binding support is achieved. Most surgeons fell these surgical glues greatly facilitate surgery for acute aortic dissection by strengthening tenuous tissues, obliterating the false lumen and improving hemostasis.